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981s lumpish ride under 3500 revs


Herbie33

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Whereabouts are you. ?  May well be someone near you with a scanner who could have a quick look. 
 

for a misfire a 15 quid Amazon unit would show up any “p” (powertrain) codes of course anything deeper or more complicated will need more grown up equipment and experience but you might be able to save yourself a few quid for the price of a pint to someone nearby. 
 

have a look at the map topic in the technical section.  You may find someone local.  

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Could be the variable valve solenoid. Mine ran so rough I thought the engine was going to fall out. The Porsche assist guy scanned the codes and said 4 cylinders were misfiring. Fixed under warranty in a couple of days

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Hi all,

so bit of an update, OPC tech took it out and then put it on computer to see if there was any codes, they couldn’t find anything wrong, they then asked their “lead” driver (senior delivery/pick up driver) to take it out, following a number of calls and his test drive he confirms there is in his words a “flutter and then a bit of a shove”

still no codes so they’ve got the car for most of next week to see if they can track down the error.

Can’t fault Cambridge OPC for their investigation as they could easily have said nowt wrong mate off you go 

so fingers crossed they’ll track down the issue and I’ll soon get it back.

 

 

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They need to log the values for throttle position sensor, cam and crank  position and other mixture, fuel, and throttle related values in real time. 

I really hate “no codes” as an excuse. that just means the car didn’t think anything wrong. A bit like a temp sensor that reads -20 to plus 50 in 2 mins or a lateral motion sensor that reads 2g when standing still.  Car doesn’t think that’s unreasonable unless someone programmed it to think that way. It’s just  that is what it saw and responds accordingly.  

 Plugging in after the event in these kind of cases is like burning a building to the ground and then asking someone what channel the tv was on three weeks ago.  
 

Live data for key engine params when “flutter and shove” occurs will tell them 100 times more than “computer says no”  and in my opinion they should be all over that, check the codes for sure but be ready to deal with “nothing reported” 
 

 

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1 minute ago, Paul P said:


 Plugging in after the event in these kind of cases is like burning a building to the ground and then asking someone what channel the tv was on three weeks ago.  
 

🤣 Like that one....right up there with "What was the cause of death?", after they've been cremated.

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5 minutes ago, Paul P said:

They need to log the values for throttle position sensor, cam and crank  position and other mixture, fuel, and throttle related values in real time. 

I really hate “no codes” as an excuse. that just means the car didn’t think anything wrong. A bit like a temp sensor that reads -20 to plus 50 in 2 mins or a lateral motion sensor that reads 2g when standing still.  Car doesn’t think that’s unreasonable unless someone programmed it to think that way. It’s just  that is what it saw and responds accordingly.  

 Plugging in after the event in these kind of cases is like burning a building to the ground and then asking someone what channel the tv was on three weeks ago.  
 

Live data for key engine params when “flutter and shove” occurs will tell them 100 times more than “computer says no”  and in my opinion they should be all over that, check the codes for sure but be ready to deal with “nothing reported” 
 

 

Thanks for that, helpful summary I’ll ask them tomorrow what they’re doing to try and identify the problem 

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So, OPC rang with an update, still can’t find anything wrong (no codes)! I did ask if they’ve run diagnostics whilst driving but they didn’t know just kept referring to the fact there are no fault codes.

They think it might need to “learn my driving style” so could I do another 500 miles and if it still does it bring it back, I told them I’ve done over 1500 miles in it since I’ve had it, think it would have learnt by now!

They’re now going to get their gold tech to look at it and call me, I can feel an argument coming on tomorrow 

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There is a little hesitancy/flutter around 2500-3000rpm, feels like a single misfire that goes away after one missed spark, very minor nothing heavy but just about noticeable if your looking for it or your senses are on alert after a problem. I had it in my old 981 2.7 and thought it was a fault but investigations ruled out any issue. Then I got the 3.4S and it has the same little blip at a similar rev. Solution is to drive it harder so your race past that point and you never notice it :) I think its down to the change in cam profiles which happen around that rev range. 

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15 hours ago, CMA said:

think its down to the change in cam profiles which happen around that rev range. 

I can’t say I’ve noticed this, but maybe if it’s subtle it could be there without me noticing.  Like most things, once you notice them even the most minor issues seem to stand out like a sore thumb.  However I thought the cams changed a bit higher than 2.5-3k, there is a distinct change of character around 4K that I always assumed was the cam profile change?.

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1 hour ago, Greenman said:

I can’t say I’ve noticed this, but maybe if it’s subtle it could be there without me noticing.  Like most things, once you notice them even the most minor issues seem to stand out like a sore thumb.  However I thought the cams changed a bit higher than 2.5-3k, there is a distinct change of character around 4K that I always assumed was the cam profile change?.

It is very subtle and only really noticeable when diving like miss daisy on light'ish throttle. I think its down to the VarioCam and Variocam Plus (one is timing one is valve lift) and I guess by their names they don't come in at a certain rev point all the time and they both work together in some pattern to decide on what timing and lift are needed depending on driving style and load. Pop it in sport and it's not as noticeable. Hoof it from low revs and you don't notice it at all. Ive experienced the same in the 4 981s I've driven so far (2 owned, 2 on test drives). 

Maybe the 4k you notice is more or the valve lift being increased with a mix of valve timing too as it knows you want to get to the horizon as quick as possible?

Don't go looking for it if you haven't noticed it or it will bug you for ever more :)

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